Evidence for a steepening of geothermal gradients in some deep mines and drill holes

Abstract

Direct readings of rock temperatures taken along the line of the new Yates Shaft of the Homestake Mine disclose a geothermal gradient that steepens notably in depth. Comparison of these results with those from several other deep mines and deep drill holes suggests that this steepening may be a general effect to the depths penetrated by those mines and drill holes. A possible cause is a gradual decrease in thermal conductivity of rocks in depth due to a gradual decrease in the amount of intergranular moisture in the rocks.